EP1058959A1

EP1058959A1 - Method and apparatus for communicating battery pack information

Info

Publication number: EP1058959A1
Application number: EP99903038A
Authority: EP
Inventors: Ivan N. Wakefield; Timothy J. Banyas
Original assignee: Ericsson Inc
Current assignee: Ericsson Inc
Priority date: 1998-02-25
Filing date: 1999-01-11
Publication date: 2000-12-13
Anticipated expiration: 2019-01-11
Also published as: JP2002505514A; BR9908150A; KR20010041362A; EE200000493A; MY123238A; US6031353A; KR100573824B1; EP1058959B1; AU2315499A; CN1292163A; AU753850B2; WO1999044268A1

Abstract

Information about a battery pack, such as the battery pack type of the battery pack, is communicated to a recharging device, preferably a wireless communications device such as a cellular telephone, via an information signal generated by the battery pack so that the recharging device may automatically distinguish between a plurality of different battery pack types to identify the type of an attached battery pack. The identification signal may be a repeating type having a fixed frequency between a low voltage level and a high voltage level and a dwell time at the high value. The identification signal is communicated to the recharging device and averaged over time. The averaged identification signal is compared against a reference signal, such as the voltage level of the battery, to determine a ratio therebetween. A logic circuit portion of the recharging device, such as a microprocessor, then identifies the battery pack type of the battery pack based on this ratio by comparing the ratio to one or more predetermined values where each of the predetermined values is associated with a battery pack type. Based on the battery pack type identified, the recharging device adjusts its charging profile or otherwise optimizes its operational characteristics. Further, the identification may instead be based on some characteristic of the identification signal itself, such as duty cycle or time at a particular voltage level. In addition, the identification signal may be continuously generated or may be generated periodically, or for some short period of time following certain events such as a power-up or battery pack changeover. In some embodiments, the identification signal may contain additional or alternative information concerning the battery pack such as an indication of the number of recharge cycles the battery pack has been through.

Description

METHOD AND APPARATUS FOR COMMUNICATING BATTERY PACK

INFORMATION

Field of the Invention

The present invention relates generally to accessories for wireless

communications devices, and more particularly to a method and apparatus for

identifying battery pack types in wireless communications devices.

Background of the Invention

Wireless communications devices, such as cellular telephones, may have a

wide variety of accessories. Examples of accessories include battery packs, hands-

free operation adapters, plug-in memory cartridges, and so forth. These various

accessories, when connected to the wireless communications device, expand the

device's capabilities.

When using the accessories, there is a great need to identify which type of

accessory is being used so that operation may be optimized. For instance, the

variety of rechargeable batteries for portable wireless communications devices have

increased over time and continues to grow. Numerous different battery cell

chemistries have been employed such as Lithium, Nickel Cadmium (NiCd), Nickel

Metal Hydride (NiMH), and Alkaline. These battery cells are typically assembled into

battery packs having various numbers of cells and overall capacities. Different

battery pack types typically have different charge capacities and optimum charging

profiles. Attempting to recharge a battery pack using a different profile may not only

diminish battery life and efficiency, but may also create a hazard due to

overcharging and overheating. As such, it is desirable for a battery charger, internal or external to a wireless communications device, to know which type of battery pack

is being recharged.

Further, different battery packs exhibit different end of life voltage and other

operational characteristics. As such, knowledge of the type of battery pack may be

useful to wireless communications devices in regulating operational parameters

such as transmitter output power or in warning the user of a "low battery" condition.

Thus, there remains a need for an inexpensive apparatus and method to

automatically determine the type or class of battery pack so that charging or

operational characteristics may be optimized. Preferably, the battery charger

automatically recognizes the battery pack type being charged and adapts its

charging and/or operational parameters accordingly.

Summary of the Invention

The present invention provides a method and apparatus for automatically

communicating information about a battery pack to a recharging device.

Typically, such information is the battery pack type of the battery pack. Thus,

by using the present invention, a recharging device may distinguish between a

plurality of different battery pack types to identify the type of an attached

battery pack.

In one preferred embodiment, an identification signal is generated by a

battery identification circuit internal to the battery pack. This identification

signal is a repeating type having a fixed frequency between a low voltage level

and a high voltage level and a dwell time at the high value. Further, the battery

pack generates a reference signal which is preferably the voltage level of the

battery. The identification signal is communicated to the recharging device and

2 averaged over time. The averaged identification signal is compared against the

reference signal to determine a ratio therebetween. A logic circuit portion of the

recharging device, such as a microprocessor, then identifies the battery pack

type of the battery pack based on this ratio by comparing the ratio to one or

more predetermined values where each of the predetermined values is

associated with a battery pack type. Based on the battery pack type identified,

the recharging device adjusts its charging profile or otherwise optimizes its

operational characteristics. Preferably, the recharging device is a wireless

communications device, such as a cellular telephone. In alternative

embodiments, the frequency may not be fixed across battery pack types.

Further, the identification may not be based on a ratio, but instead on some

characteristic of the identification signal itself, such as duty cycle or time at a

particular voltage level. In addition, the identification signal may be continuously

generated or may be generated periodically, or for some short period of time

following certain events such a power-up or battery pack changeover. In some

embodiments, the identification signal may contain additional or alternative

information concerning the battery pack such as an indication of the number of

recharge cycles the battery pack has been through.

Brief Description of the Drawings

FIGURE 1 is a simplified functional block diagram of a battery pack and a

wireless communications device of the present invention.

FIGURE 2 is a simplified functional block diagram of an alternative battery

pack configuration. FIGURE 3 is a first example of an identification signal of the present invention

having a squarewave waveform.

FIGURE 4 is a second example of an identification signal of the present

invention having a squarewave waveform.

FIGURE 5 is a simplified functional block diagram of a battery pack of the

present invention which includes a logic circuit between the battery and the battery

identification circuit and a wireless communications device of the present invention

without a filtering circuit.

Detailed Description

The present invention utilizes an identification circuit 110 associated with a

battery pack 100 to generate an identification signal indicative of the battery pack

type. This identification signal is communicated to a wireless communications

device 10 which, in a preferred embodiment, identifies the battery pack 100 type

based on a ratio of the identification signal to a reference signal. Based on the

battery pack 100 identified, the wireless communications device 10 adjusts the

parameters of an included battery charging circuit 18 for optimum charging of that

type battery pack 100.

A wireless communications device 10, such as a cellular telephone, is shown

in Figure 1. The wireless communications device 10 typically includes an antenna

12 coupled to a transceiver 14, a microprocessor 16, a battery charging circuit 18,

and electrical terminals 22,24,26 for connection to the battery pack 100. The

microprocessor 16 controls the overall function of the wireless communications

device 10. The transceiver 14 encodes and decodes communication and control

signals which are transmitted and received via the antenna 12. The battery charging

4 circuit 18 converts power received from an external power source at an external

power terminal 28 to a form suitable for recharging a battery pack 100. The battery

charging circuit 18 operates under the control of the microprocessor 16. When the

wireless communications device 10 is not coupled to external power, the wireless

communications device 10 receives power from the battery pack 100 via a plurality

of terminals 22,24. Further details of the wireless communications device 10

arrangement and functioning are well known in the art and are not important to

understanding the present invention.

In one particular embodiment, the microprocessor 16 includes at least two

analog to digital (A/D) ports 32,34 and a ground port 36. The ground port 36 is

connected to a ground terminal 22. The first A/D port 32, called the reference power

port, is connected to a positive power terminal 24. The second A/D port 34, called

the ID signal port, is connected to an identification terminal 26 via a RC filter circuit

40. The RC filter circuit 40 includes a resistor 42 and a capacitor 44 connected as

shown in Figure 1.

The battery pack 100 includes a battery 102, a battery identification circuit

110, and a plurality of terminals 122,124,126. The battery 102 may be composed of

one or more battery cells connected in a manner well known in the art. The negative

or ground portion of the battery 102 is connected to a ground terminal 122. The

positive portion of the battery 102 is connected to a battery identification circuit 110

and to the positive power terminal 124. The battery identification circuit 110 is

connected to both the positive portion of the battery 102 and the negative portion of

the battery 102 and to the identification terminal 126. The battery identification circuit 110 includes a capacitor 112, a plurality of

resistors 113, 114, a diode 116, and an inverter 118 (preferably of a low current

consumption type such as a Schmitt inverter) connected as shown in Figure 1. The

battery identification circuit shown in Figure 1 functions for duty cycles above 50%.

One alternative arrangement of the battery identification circuit 110 for duty cycles

below 50% is shown in Figure 2, wherein the sense of diode 116 is reversed with

respect to that shown in Figure 1.

When the battery pack 100 is coupled to the wireless communications device

10, the terminals 22,122,24,124,26,126 make electrical contact. That is, ground

terminal 22 is electrically connected to ground terminal 122, positive power terminal

24 is electrically connected to positive power terminal 124, and identification terminal

26 is electrically connected to identification terminal 126. In battery power mode,

main power to the wireless communications device 10 is provided via ground

terminals 22,122 and positive power terminals 24,124 in a manner well known in the

art.

In addition, the battery identification circuit 110 generates an identification

signal which is communicated to the wireless communications device 10 via the

identification terminals 26,126. In a first embodiment, this generated identification

signal varies over time at a fixed frequency, but has a variable duty cycle. An

example of two possible identification signals are the squarewave waveforms shown

in Figure 3 and Figure 4. As shown in the figures, the time from the start of one

wave to the start of the next is constant, thereby defining a fixed frequency. The two

identification signals of Figure 3 and Figure 4 are differentiated by their duty cycles,

that is the time spent at the high voltage. The identification signal of Figure 3 has a

6 dwell time at the high voltage level of % of the period of the wave, thus its duty cycle

is % (75 %). The identification signal of Figure 4 has a dwell time at the high voltage

level of 2 the period of the wave, thus its duty cycle is V2 (50 %). While two

examples of the identification signal are shown in Figures 3 and 4, a wide variety of

duty cycles are possible. The number of different duty cycles may be limited by the

frequency employed and the resolution of the generation and detection electronics,

including slew rates.

When power is applied to the battery identification circuit 110 of Figure 1 , the

energy stored in capacitor 112 is zero. Therefore, the voltage applied to the inverter

118 will be ground; consequently, the inverter 118 outputs a high voltage level. This

high voltage level begins to charge up capacitor 112 through resistor 113.

Eventually, the capacitor 112 will charge up, causing the input voltage to the inverter

118 to exceed logical high. When this happens, the inverter 118 will output a low

voltage level, which in turn causes capacitor 112 to discharge through resistors 113

and 114. As capacitor 112 discharges, the voltage level to the inverter 118 will

decrease. When the voltage to the inverter 118 falls below the logical low level, the

inverter 118 will output a high voltage level. This cycle will repeat itself indefinitely

for the battery identification circuit 110 of Figure 1.

The particular identification signal generated by the battery identification

circuit 110 will depend on the characteristics of the components of the battery

identification circuit 110. By controlling the charge and discharge times of the

capacitor 112, through the selection of the combination of capacitor 112, resistor

113 and resistor 114, the duty cycle and frequency of the generated identification

signal may be controlled. Examples of various combinations are given below:

7 Capacitor Resistor Resistor Frequency Duty Cycle

112 113 114

10 nf 34 kΩ 9.8 kΩ 5 kHz 80 %

10 nf 25 kΩ 38 kΩ 5 kHz 60 %

10 nf 22.7 kΩ 60.4 kΩ 5 kHz 40 %

10 nf 30 kΩ 11.3 kΩ 5 kHz 20 %

The battery identification circuits 110 shown in Figure 1 and Figure 2 are

examples of circuits suitable for generating the battery identification signal.

However, any circuit which outputs a constant frequency wave with varying duty

cycles would function equivalently and is encompassed herein. Preferably, the

waveform generated has a squarewave waveform. It is preferred that the battery

identification circuit 110 consume very little power, such as less than 10 μA.

The difference in duty cycles allows the wireless communications device 10 to

determine which type of battery pack 100 it is coupled to. The battery identification

signal is received at the identification terminal 26 and filtered by the RC filter circuit

40. The RC filter circuit 40 smoothes the identification signal to produce a steady

voltage level signal with the voltage level being the average of the identification

signal generated by the battery identification circuit 110. This voltage level is

communicated to the ID signal port 34 on the microprocessor 16. In addition, the

battery voltage level is communicated to the reference power port 32 via the positive

power terminals 24, 124. The microprocessor 16 then compares the voltage levels

at the ID signal port 34 and the reference power port 32 and determines the relative ratio therebetween. Based on this ratio, the microprocessor 16 consults a lookup table of battery pack types and their corresponding duty cycles to determine what

type of battery pack 100 is coupled to the wireless communications device 10.

Once the battery pack type is determined, the wireless communications

device 10 may make any adjustments required to the battery charging circuit 18 for

optimum battery charging and/or may change other operational characteristics such

as transmit power level.

Note that the term "battery pack type" as used herein means the combination

of battery cell chemistry/composition and the number and size of such cells in a

battery pack 100. For instance, one battery pack type could be four size A lithium

battery cells, another battery pack type could be six size A lithium battery cells, and

still another battery pack type could be one size C NiCd battery cell.

The term "recharging device" includes stand alone battery pack rechargers

which draw power from external power sources, such as a wall outlet, and wireless communications devices which include battery recharging circuits 18. Note that

stand alone battery rechargers may also perform other functions such as facilitating

hands-free operation of wireless communications devices.

The discussion above has assumed that the battery pack 100 is coupled to a

wireless communications device 10, which in turn includes the RC filter circuit 40,

battery charging circuit 18, and microprocessor 16. However, the present invention

also functions when the RC filter circuit 40, battery charging circuit 18, and

microprocessor 16 are part of a stand-alone battery charger. These components

function in the same manner as described above and the battery identification signal is handled as described above. Based on the ratio of the identification signal to the

9 reference battery signal, the battery charger identifies the battery pack type and adjusts charging parameters accordingly.

The discussion above has used a microprocessor 16 as an example of a logic

circuit that performs the comparison of voltage levels and the identification of the

battery pack type via the lookup table. However, a microprocessor 16 need not be

employed. Instead, dedicated discrete logic circuits may be used or other circuits

within the wireless communications device may be used to perform equivalent functions.

In the discussion above, the battery identification signal has a fixed frequency

across battery pack types and the battery identification signal is compared against a

reference signal on a voltage ratio basis. However, the present invention does not

require that the battery identification signal have a fixed frequency across battery

pack types. The comparison against a reference signal on a voltage basis will work

equally well at a plurality of frequencies, provided that the ratio of the battery

identification signal average voltage to the reference signal voltage remains

indicative of the battery pack type.

Furthermore, alternative embodiments of the present invention do not require

a reference signal. Instead, the characteristics of the battery identification signal

itself are examined to identify the battery pack type. For instance, the RC filter

circuit 40 may be omitted and the battery identification signal may be directly routed

to the microprocessor 16. See Figure 5. The microprocessor 16 may digitally

sample the battery identification signal and monitor the ratio of high voltage level to low voltage level of the battery identification signal, thereby monitoring the duty cycle

of the battery identification signal. The digital sampling rate should be at a

10 frequency significantly higher than the frequency of the battery identification signal.

Based on the duty cycle of the battery identification signal, the battery pack type is

identified as described above. Alternatively, the absolute time that the battery

identification signal is at a certain logical voltage level, such a logical high, may be

monitored by the microprocessor 16 and different times may be used to identify

different battery pack types.

An alternative arrangement of the battery pack 100, which includes an

additional logic circuit 130, is shown in Figure 5. The logic circuit 130 controls the

operation of the battery identification circuit 110. The logic circuit 130 may, for

example, control the battery identification circuit 110 such that the battery

identification signal is not generated continuously. For instance, the battery

identification signal may be generated periodically, or for some short period of time

following certain events such a power-up or battery pack 100 changeover. In

addition, the logic circuit 130 may cause the battery identification signal to be

indicative of some characteristic of the battery pack other than simply battery pack

type. For instance, the battery identification signal may be used to indicate the

number of recharge cycles the battery pack 100 has been through, battery

temperature, remaining capacity, a low voltage condition, or the like.

The present invention encompasses any wireless communications device 10

which is powered by any one of multiple different types of battery packs 100.

Examples include cellular telephones, personal communications assistants, pagers,

and the like. Also, as mentioned above, a stand alone battery charger may take the

place of the wireless communications device 10.

11 The present invention may, of course, be carried out in other specific ways

than those herein set forth without departing from the spirit and essential

characteristics of the invention. The present embodiments are, therefore, to be

considered in all respects as illustrative and not restrictive, and all changes coming

within the meaning and equivalency range of the appended claims are intended to

be embraced therein.

12

Claims

1 . A method for communicating information about a battery pack for a

wireless communications device, comprising:

a) generating, at said battery pack, a repeating information signal

having a frequency between a low value and a high value and a

dwell time at said high value; and

b) determining one or more characteristics of said battery pack

based on said information signal.

2. The method of claim 1 wherein said characteristic is the battery pack

type of said battery pack.

3. The method of claim 1 wherein said generating of said repeating

information signal is for a predetermined time interval and then stops.

4. The method of claim 3 wherein said predetermined time interval is 10

seconds.

5. The method of claim 1 wherein said determining is based on the duty

cycle of said information signal.

6. The method of claim 1 wherein said determining is based on said dwell

time at said high value.

7. The method of claim 1 further including generating, at said battery

pack, a reference signal and wherein said determining is based on the ratio of

said information signal to said reference signal.

8. The method of claim 7 wherein said battery pack belongs to one of a

plurality of battery pack types and wherein said frequency is the same for a

plurality of said battery pack types.

13

9. A method for distinguishing between a plurality of different battery

pack types to identify the type of a battery pack, comprising:

a) generating, at said battery pack, a repeating identification signal

having a frequency between a low value and a high value and a

dwell time at said high value; and

b) identifying the battery pack type of said battery pack based on

said identification signal.

10. The method of claim 9 wherein said generating of said repeating

identification signal is for a predetermined time interval and then stops.

1 1 . The method of claim 10 wherein said predetermined time interval is

1 5 seconds.

12. The method of claim 9 wherein said identifying is based on the duty

cycle of said identification signal.

13. The method of claim 9 wherein said identifying is based on said

dwell time at said high value.

14. The method of claim 9 further including generating, at said battery

pack, a reference signal and wherein said determining is based on the ratio of

said identification signal to said reference signal.

1 5. A method for distinguishing between a plurality of different battery

pack types to identify the type of a battery pack, comprising:

a) generating, at said battery pack, a repeating identification signal

having a fixed frequency between a low value and a high value

and a dwell time at said high value;

b) generating a reference signal;

14 c) determining the ratio of said identification signal to said reference

signal; and

d) identifying the battery pack type of said battery pack based on

said ratio by comparing said ratio to one or more predetermined

values; each of said predetermined values being associated with

a battery pack type.

16. The method of claim 1 5 wherein said low value and said high value

are different voltage levels.

17. The method of claim 16 wherein said ratio is the based on the

average voltage value of said identification signal.

18. The method of claim 1 5 wherein said reference signal is the present

voltage level of said battery pack.

19. The method of claim 1 5 wherein a wireless communications device

performs said comparing and said identifying.

20. A method for distinguishing by a recharging device between a

plurality of different battery pack types to identify the type of a battery pack,

comprising:

a) generating, at said battery pack, a repeating identification signal

having a fixed frequency between a low voltage level and a high

voltage level and a dwell time at said high value;

b) generating, at said battery pack, a reference signal representing

the present voltage level of said battery;

c) averaging said identification signal;

15 d) comparing, by a recharging device, said averaged identification

signal to said reference signal to determining the ratio of said

averaged identification signal to said reference signal; and

e) identifying, by said recharging device, the battery pack type of

said battery pack based on said ratio by comparing said ratio to

one or more predetermined values; each of said predetermined

values being associated with a battery pack type.

21 . The method of claim 20 wherein said recharging device is a

wireless communications device.

22. The method of claim 21 wherein said wireless communications

device is a cellular telephone.

23. The method of claim 20 wherein said recharging device is a stand

alone battery pack recharger.

24. The method of claim 20 wherein said generation of said

identification signal is by a circuit having at least a diode, an inverter, a

capacitor, and a plurality of resistors.

25. A device for communicating information about a battery pack for a

wireless communications device, comprising:

a) a battery identification circuit; said battery identification circuit

generating a repeating information signal at said battery pack

having a frequency between a low value and a high value and a

dwell time at said high value; and

b) a logic circuit external to said battery pack; said logic circuit

monitoring said information signal and determining one or more

16 characteristics of said battery pack based on said information

signal.

26. The device of claim 25 wherein said battery pack belongs to one of

a plurality of battery pack types and wherein said characteristic is the battery

pack type of said battery pack.

27. A battery pack type identifier for distinguishing between a plurality

of different battery pack types to identify the type of a battery pack, comprising:

a) a battery identification circuit; said battery identification circuit

generating a repeating identification signal at said battery pack

having a frequency between a low value and a high value and a

dwell time at said high value; and

b) a logic circuit external to said battery pack; said logic circuit

monitoring said identification signal and identifying the battery

pack type of said battery pack based on said identification signal.

28. The battery pack identifier of claim 27 wherein said logic circuit

monitors the duty cycle of said identification signal and identifies the battery

pack type of said battery pack based on said duty cycle.

29. The battery pack identifier of claim 27 wherein said logic circuit

monitors the said dwell time of said identification signal and identifies the

battery pack type of said battery pack based on said dwell time.

30. A battery pack type identifier for distinguishing between a plurality

a) a battery pack including a battery identification circuit; said

battery identification circuit generating a repeating identification

17 signal at said battery pack having a frequency between a low

value and a high value and a dwell time at said high value;

b) a reference signal; and

c) a logic circuit external to said battery pack; said logic circuit

monitoring said identification signal and said reference signal and

computing a relative ratio thereof; and

d) wherein the battery pack type of said battery pack is identified

by said logic circuit based on said ratio.

31 . The battery pack identifier of claim 30 wherein said logic circuit

further identifies said battery pack type by comparing said ratio to one or more

predetermined values; each of said predetermined values being associated with a

battery pack type.

32. The battery pack type identifier of claim 30 further including a

filtering circuit between said battery identification circuit and said logic circuit;

said filtering circuit averaging said identification signal.

33. The battery pack type identifier of claim 30 further including a

battery recharging device in communication with said battery pack.

34. The battery pack type identifier of claim 30 wherein said battery

identification circuit includes at least a diode, an inverter, a capacitor, and a

plurality of resistors.

35. A battery pack type identifier for distinguishing between a plurality

a) a battery pack including:

18 i) a battery identification circuit; said battery

identification circuit generating an identification signal

having a fixed frequency between a low value and a

high value and a dwell time at said high value;

ii) a first positive power terminal, a first ground terminal,

and a first identification terminal;

b) a reference signal;

c) a recharging device including:

i) a filtering circuit; said filtering circuit generating an

average of said identification signal;

ii) a microprocessor logic circuit for comparing said

average identification signal to said reference signal

and generating a ratio thereof;

iii) a second positive power terminal, a second ground

terminal, and a second identification terminal;

d) wherein said first positive power terminal is connected to said

second positive power terminal, said first ground terminal is

connected to said second ground terminal, said first

identification terminal is connected to said second identification

terminal;

e) wherein said identification signal is communicated from said

battery pack to said recharging device via said first identification

terminal; and

19 f) wherein said battery pack type is identified based on said ratio

by comparing said ratio to one or more predetermined values;

each of said predetermined values being associated with a

battery pack type.

36. The battery pack type identifier of claim 35 wherein said recharging

device is a wireless communications device.

37. The battery pack type identifier of claim 36 wherein said wireless

communications device is a cellular telephone.

38. The battery pack type identifier of claim 35 wherein said recharging

device is a stand alone battery pack recharger.

39. The battery pack type identifier of claim 35 wherein said battery

plurality of resistors.

40. The battery pack type identifier of claim 35 wherein said filtering

circuit includes at least a capacitor and a resistor.

41 . The battery pack type identifier of claim 35 wherein said logic

circuit is a microprocessor.

42. The battery pack type identifier of claim 35 wherein said battery

pack further includes a battery pack logic circuit in communication with said

battery identification circuit and wherein said battery pack logic circuit causes

said battery pack identification circuit to cease generating said identification

signal after predetermined interval of time.

20